Numerical Simulation of the Gasoline Spray with an Outward-Opening Piezoelectric Injector: A Comparative Study of Different Breakup Models

The outward-opening piezoelectric injector can achieve stable fuel/air mixture distribution and multiple injections in a single cycle, having attracted great attentions in direct injection gasoline engines. In order to realise accurate predictions of the gasoline spray with the outward-opening piezoelectric injector, the computational fluid dynamic (CFD) simulations of the gasoline spray with different droplet breakup models were performed in the commercial CFD software STAR-CD and validated by the corresponding measurements. The injection pressure was fixed at 180 bar, while two different backpressures (1 and 10 bar) were used to evaluate the robustness of the breakup models. The effects of the mesh quality, simulation timestep, breakup model parameters were investigated to clarify the overall performance of different breakup model in modeling the gasoline sprays. It is found that the tuned Reitz-Diwakar (RD) model shows robust performance under different backpressures and the spray penetration shows good agreement with the experimental measurements. However, the modified Kelvin-Helmholtz (KH) Rayleigh-Taylor (RT) model could not achieve good agreements with fixed model parameters at different backpressures. The tuned KHRT model at 1 bar backpressure shows much faster breakup process at 10 bar backpressure, leading to abnormal spray patterns and fuel vapor distributions. As there is no further tuning requirement for different backpressures, the RD model is found to be better in modeling the gasoline sprays from the outward-opening piezoelectric injector.